Reserve - please suggest

Hi,
I am looking to buy a reserve parachute. My in flight weight is around 89 kg ( 69kg nude weight + 20kg - harness+helmet+others). What should be ideal weight category for my reserve? (Please note that someone suggested that even a 120kg reserve will be good for me and I am not sure if it will work for me.) ( I am currently doing normal flying and no acros).

Please also suggest some links to read/view more about reserves?

Thanks.